Over time, with repeated braking operations, the friction elements, and to a lesser extent the brake rotor, of disc brakes will wear down and need to be replaced in order for the disc brake assembly to continue to provide adequate braking. Many air actuated disc brakes, for use on heavy vehicles, have an adjuster mechanism to set the position of the friction elements relative to the brake rotor to account for the wear of the friction material thereof, whilst maintaining a suitable running clearance to the rotor.
When the friction elements (commonly known as brake pads) are fully worn, these can be replaced with new thicker elements. If the friction elements are replaced too early when a substantial thickness of friction material remains, the operating costs of the vehicle are increased. Whereas, if replacement of the friction elements occurs too late, after the elements have become excessively worn and the friction material is no longer remaining, the resulting braking effect may be insufficient and/or may result in damage to the disc brake assembly.
Due to this, the operator needs to be able to monitor the amount of wear that has occurred to the friction elements. Typically, a visual wear indicator is provided on the disc brake assembly to enable the operator to visually check the wear of the elements. In some installations, air actuated disc brakes are fitted with electrical continuous wear sensors which monitor the wear of the friction elements. However, a visual indicator is still desirable in such systems.
Typically, the visual wear indicator is provided in the form a spring loaded pin which extends through, and protrudes from an inboard face of the caliper and abuts an inboard face of the brake carrier. As the friction elements are worn down, the pin moves outboard and the amount protruding from the caliper reduces.
Such systems require machining of the caliper so as to accommodate the pin, and also require these additional pin and spring components, adding to expense. Furthermore, depending upon the particular brake installation, the pin may be difficult to view with a wheel fitted to the brake. This makes visual inspection of the wear inconvenient.
The present invention seeks to overcome or at least mitigate some or all of the problems associated with the prior art.